1. Field of the Invention
The present invention relates to a television receiver having a motion detector which detects the motion of images represented by received television signals, and more particularly to a television signal processor which receives video signals having a greater aspect ratio than that of the conventional television system having a 4:3 aspect ratio (the ratio of horizontal to vertical length), and which also regenerates television signals compatible with the conventional television system.
2. Description of the Prior Art
More than 36 years have passed since the color television broadcasting of the present NTSC (National Television System Committee) system started in the U.S.A. in 1954. During this peroid of time, various television systems have been advocated to meet the requirement for high-definition video images, following the improvement of the television receivers. TV programs are also changed from those originating in studios and by relay broadcasting to movies of cinema size which has video images of higher-definition accompanied with vivid reality.
The present broadcasting has specifications such as 525 scanning lines, an interlace scanning of 2:1, a luminance signal horizontal bandwidth of 4.2 MHz, and aspect ratio of 4:3 (Refer to "US Color Television Fundamentals-A Receiver", IEEE Trans. Consum. Electron., Vol. CE-23, pp. 467-478, Nov. 1977). When a movie is broadcast as a TV program, it is transmitted so that both left and right ends of its video image are cut off to make its aspect ratio 4:3 which fits the present television receiver, or so that image invalid areas are provided at upper and lower parts of an image plane to make an image valid area have the aspect ratio of movies.
As described above, when movies or other programs with vivid reality are transmitted or broadcast, a part of the video image is cut off, or the area of the video image is made smaller, such that the idea and intent of the producer or the director not be fully understood. If signals of an aspect ratio greater than 4:3 are transmitted as is, a usual receiver can not receive them. If the aspect ratio is m:3 ( where m is a real number greater than 4), a video signal band of m/4 times is required in order to obtain the same horizontal resolution as the present broadcast system when the number of scanning lines and frame frequency are the same as that of the present broadcast system. But in order to effectively utilize the radio wave resources, the transmitting band should not be merely expanded.
Therefore, a television receiver which receives a video signal having an aspect ratio of more than 4:3, namely, of a wide aspect ratio, has been proposed (for example, refer to Japanese Laid-Open Patent Publication No. 63-36681).
In order to explain the conventional television signal processor, a method in which images of a wide aspect ratio are transmitted and received is discussed below.
FIG. 10 shows a signal process to transmit an image having a wide aspect ratio. A transmission side forms a main signal by time multiplexing a signal which is formed by expanding with respect to time a portion having an aspect ratio of 4:3 (a center panel portion), and a signal which is formed by compressing with respect to time of low frequency components of portions having an aspect ratio of other than 4:3 (side panel portions). This main signal is subjected to a vestigial sideband amplitude modulation with a video carrier. This television signal, which is the vestigial sideband amplitude modulated signal, is properly multiplexed by a signal (multiplex signal) which is formed by expanding with respect to time of a high frequency component of the side panel portions, and is then transmitted. At a reception side, the television signal is separated and demodulated into the main signal and the multiplex signal to regenerate the image having a wide aspect ratio by doing the reverse of the process at the transmission side. The reception side has a YC separation circuit and a scan-converter circuit in order to obtain images of a high definition. In order to control the YC separation circuit and the scan-converter circuit, a motion detection circuit is required which respectively detects motion information of the main and multiplex signals (see Japanese Laid-Open Patent Publication No. 58-130685).
However, in the television signal processor receiving the image having a wide aspect ratio of the above configuration, the conventional motion detection circuit can not acquire a satisfactory high-definition image. If an object is moved, for example, in the horizontal direction, a spectral distribution of the low frequency components of the side panel portions is different from that of the center panel portion because the low frequency components of the side panel portions are compressed with respect to time before being transmitted, so that a motion detection signal of the center panel portion is different from a motion detection signal of the side panel portions. The high frequency components of the side panel portions are expanded with respect to time and then transmitted, so that a motion detection signal of the side panel portions is also different from that of the center panel portion. As a result, there is a problem that quality of the images at the center panel portion and the side panel portions are uneven especially when a moving image is displayed because of the difference in the motion detection signals.